The invention relates to a method for operating an internal combustion engine which has a number of cylinders and which comprises a fuel system and a fresh air system, whereby fuel is fed in a fuel mass flow via a fuel supply line of the fuel system to the cylinders at a prescribable air-fuel ratio directly by means of the injectors, and fresh air is fed in a fresh air mass flow via a fresh air system, whereby the fuel system comprises a tank venting system with a tank venting line that has a tank venting valve and that, via the interconnected tank venting valve, is connected to at least one line section of the fresh air system via at least one feed point, thereby forming at least one venting path.
German patent application DE 10 2008 042 638 A1 discloses a method for operating an internal combustion engine, whereby a crankcase of the internal combustion engine has a venting system in the intake system of the internal combustion engine. When fuel is outgassed from engine oil that is present in the crankcase, the operating point of the internal combustion engine is changed so as not to fall below a prescribable air-fuel ratio. Therefore, a crankcase venting system is being put forward with which gases are conveyed from the crankcase into the intake pipe and thus into the intake system of the internal combustion engine. In this context, it is provided, for example, to select an operating point for the air-fuel ratio—especially the rich-running limit—that has a fuel consumption that is as high as possible. The outgassing of fuel can be ascertained by monitoring and measuring the lambda value control since it can be noted that the fuel-air mixture becomes richer during the outgassing. In summary, it is provided that the load point of the internal combustion engine should be raised in order to allow a higher purging rate of fuel gases, whereby a minimum injection time is explicitly cited as the existing limit of the fuel mass flow.
European patent application EP 2 530 262 A1 discloses a control unit for an internal combustion engine in which a fuel gas is returned to the intake system. In the associated method, NOx is measured and then returned to the intake system parallel to the fuel gas. In this process, the lambda value control serves to evaluate and regulate the mass flows.
U.S. Pat. No. 5,746,187 A describes a tank venting system. A method is disclosed that controls the mass flow rate of the tank venting volumetric flow. In this process, the lambda value control likewise serves to monitor the purging quantity, whereby the injected quantity or the actuation angle of the tank venting valve is appropriately adjusted.
Before the backdrop of the state of the art, the objective of the invention is to offer a solution that allows the purging air mass flow of the tank venting system to be increased, whereby, if at all possible, no additional components are needed that would have to be additionally integrated into the tank venting system of a fuel system.